Method for recovering the energy of gas expansion and a recovery device for carrying out said method

ABSTRACT

The proposed method and the installation are intended for application in systems of reduction of natural gas from high—e.g. in a borehole or in a main pipeline down to the pressure value required for the consumer. 
     The essence of the proposed method is that in the known method of utilization of natural gas energy in the process of gas pressure drop from increased, e.g. in a gas main pipeline down to the required value by conversion of natural gas expansion energy to mechanical energy with the aid of the gas cooled down in the process of pressure drop as a cooling agent, the innovation is multi-stage gas pressure drop and multi-stage take-off of generated cold. 
     The essence of the proposed method is that a utilization power installation the inlet of which is connected to high pressure gas borehole or main pipeline ( 3 ) and the outlet—to low pressure natural gas pipeline or to low pressure natural gas consumer ( 7, 9 ), comprises a gas expansion machine (e.g. expansion gas turbine) consisting of two or more components ( 1, 2 ), arranged in the direction of pressure drop, converter ( 4 ) of mechanical energy, e.g. an with the gas expansion machine OM , and two or more heat exchangers ( 6, 8 ).

FIELD OF THE INVENTION

The proposed method and the installation are intended for application insystems of reduction of natural gas from high—e.g. in the borehole or inmain pipelines down to the pressure value required for the consumer.

BACKGROUND OF THE INVENTION

The known methods of reduction of pressure of gas in boreholes or inmain pipelines are based on throttling and using special devices(pressure regulators, valves, cocks etc) for implementation of thesemethods. [Polytechnic Dictionary, Moscow, “Sovetskaya Entsiklopedia”Publishing House, 1977, pp. 153, 420]

These methods and devices for implementation thereof do not utilizeenergy of gas expansion and cold generated during this process. Theapplication of these methods and devices requires sophisticatedequipment and consumption of additional power to prevent clogging ofpressure regulators by moisture and ice generated during theiroperation.

A method of utilization of energy of natural gas when its pressure dropsfrom the value in the main pipeline or in the borehole down to therequired pressure by conversion of gas expansion energy to mechanicalenergy is known. [RU 2117173, MΠK 6 F 02 C 1/02, 1996]. This method isimplemented in a utilization power installation the inlet of which isconnected to the outlet of the high pressure gas borehole or the mainpipeline and the outlet—to the low pressure gas pipeline or to the gasconsumer. This utilization power installation includes a gas expansionmachine, e.g. an expansion turbine, and a mechanical energy converterconnected kinematically with the gas expansion machine, e.g. an electricgenerator. Such method and the installation make it possible to utilizegas expansion energy when its pressure drops.

However this method and the installation do not provide the possibilityof utilization of: cold generated in the process of gas expansion. Theefficiency of this method and the installation is low.

There is a method of utilization of gas expansion energy when the gaspressure drops from a high value to the required one by conversion ofgas expansion energy to mechanical energy with simultaneous utilizationof the gas cooled down during pressure drop as a cooling agent forgeneration of cold. [SU, A1, 844797]

However this method provides a single-stage gas pressure drop and hencetotal efficiency thereof is reduced.

There is a power installation for utilization of gas expansion energyand the cold generated during this process. [RU 2013616, MΠK F 02 C6/00, 1994]

However efficiency of this installation is low as gas pressure reductionand utilization of cold are effected at a single stage.

DISCLOSURE OF THE INVENTION

The object of this invention is to improve utilization of cold generatedduring the process of reduction of natural gas pressure; generation ofgreat amount of energy and cold and to increase total efficiency of themethod and the installation for utilization of natural gas expansionenergy.

The problem set in the proposed method is solved by reduction of naturalgas from high—e.g. in main pipelines down to the pressure value requiredfor the consumer by conversion of gas expansion energy to mechanicalenergy by using the gas cooled down in the process of gas pressure dropas a cooling agent. The innovation of this method is reduction ofnatural gas pressure in two or more successive stages and simultaneousutilization of at least a part of gas after the first and/or after eachrespective subsequent stage of reduction of natural gas pressure as acooling agent for generation and use of cold. Another part of naturalgas after the first and/or after each respective subsequent stage ofreduction of natural gas pressure or the total amount of natural gasused as a cooling agent is used at the next stage of conversion ofnatural gas expansion energy to mechanical energy.

Due to application of the stage-by-stage reduction of natural gaspressure and the use of the total amount or a part of natural gas afterthe first and/or after the relevant subsequent stage of natural gaspressure drop the total efficiency of the method increases.

The problem set in the proposed machine is solved by implementation of ainstallation for utilization of natural gas expansion energy thatincludes a gas expansion machine, e.g. an expansion turbine, inlet ofwhich is connected to a high pressure gas borehole or main pipeline andthe outlet—to a low pressure gas pipeline; a gas expansion machine, e.g.an expansion turbine and a mechanical energy converter connectedkinematically with the gas expansion machine, e.g. an electricgenerator. There is at least one heat exchanger in this installation,the outlet branch pipe of which is connected to the outlet of the gasexpansion machine, e.g. to the, outlet of the expansion turbine.

The innovation introduced in this facility is that the gas expansionmachine of the utilization power installation, e.g. the expansionturbine, consists of two or more components arranged in the direction ofnatural gas pressure drop; the installation also comprises two or moreheat-exchangers—refrigerators; the inlet branch pipe from the coolantside of each heat-exchanger—refrigerator is connected to the outlet ofthe relevant component of the expansion machine and the number ofheat-exchangers—refrigerators is not less than the number of expansionmachine components.

This improvement of the utilization power installation ensures theincrease of efficiency of this installation and the amount of generatedcold.

The outlet of the preceding component of the gas expansion machine ofthe utilization power installation can be connected simultaneously bothto the inlet of the next component of the gas expansion machine, and tothe inlet branch pipe from the cooling agent side of the relevant heatexchanger-refrigerator, and the outlet branch pipe from the coolingagent side of one or more heat exchanger-refrigerators—to the lowpressure gas pipeline or the gas consumer. In this case the flow of theworking medium branches out and a part of the working medium is takenoff for utilization of cold. This improves the thermo-dynamical workingcycle of the installation.

Such an improvement increases the efficiency of the installation. At thesame time it becomes possible to optimally regulate the operation of thegas expansion machine when the operation mode changes.

In the utilization power installation proposed the outlet of thepreceding component of the gas expansion machine can only be connectedto the inlet branch pipe from the cooling agent side of one or each heatexchanger-refrigerator, located between two components of the gasexpansion machine, and the outlet branch pipe from the cooling agentside of the same heat exchanger-refrigerator, located between the twocomponents of the gas expansion machine, can be connected to the inletof the working medium of the next component of the gas expansionmachine. Then additional heating of the working medium (gas) occurs inone or in each heat exchanger-refrigerator. It improves thermo-dynamicalworking cycle of the installation.

This improvement increases additionally the efficiency of theinstallation and by utilization of the heat of the cooling agent, heateddue to heat exchange in the heat exchanger-refrigerator. At the sametime it becomes possible to optimally regulate the operation of the gasexpansion machine when the operation mode changes by changing the amountand/or the temperature of the working medium (liquid, gas or severalworking mediums) heated in the heat exchangers-refrigerators.

BRIEF DESCRIPTION OF DRAWINGS

In DWG. 1 the diagram of a utilization power installation is shown. Theinstallation includes an expansion gas turbine that contains a highpressure component and a low pressure component, two heatexchangers-refrigerators and an electric generator.

In DWG. 2 the diagram of a utilization power installation is shown. Theinstallation includes an expansion gas turbine that contains a highpressure component, a medium pressure component and a low pressurecomponent, three heat exchangers-refrigerators and an electricgenerator.

In DWG. 3 the diagram of a utilization power installation is shown. Theinstallation includes expansion gas turbines that contain high pressurecomponents, medium pressure components and low pressure components,three heat exchangers-refrigerators and three electric generators.

The invented method and the installation are illustrated by descriptionsof the preferred embodiments thereof the embodiments of implementationof the utilization of gas expansion energy being described in thedisclosure of operation of variants of the installation.

Variant 1. (DWG.1)

The utilization power installation includes an expansion gas turbinethat contains high pressure, components 1(HPC 1), and low pressurecomponents 2 (LPC 2) arranged co-axially. The inlet of HPC 1 isconnected to high pressure gas main pipeline 3. This main pipeline 3 canbe a high- or medium-pressure natural gas pipeline, a gas pipeline ofthe gas distribution station, a thermal power station, a boiler house, aborehole in the natural gas production site etc. (These facilities arenot shown in the drawings). Electric generator shaft 4 that supplieselectric power to consumer 5 is connected kinematically or directly tothe common shaft of HPC 1 and LPC 2. The outlet of HPC 1 is connectedboth to the inlet of LPC 2, and the inlet branch pipe from the coolingagent side of heat exchanger-refrigerator 6. The outlet of the branchpipe from the cooling agent side of heat exchanger-refrigerator 6 isconnected to the low pressure gas pipeline through which gas is suppliedto consumer 7.

Heat exchanger-refrigerator 8 is installed at the gas outlet of LPC 2 ofthe expansion gas turbine. The inlet branch pipe of the heatexchanger-refrigerator from the cooling agent side is connected to thegas outlet out of LPC 2 of the expansion gas turbine and the outletbranch pipe from the cooling agent side of the heatexchanger-refrigerator 8 is connected to the low pressure gas pipeline,that supplies gas to consumer 9.

The utilization power installation operates in the following way. Highpressure natural gas flows out of main pipeline 3 into HPC 1, rotatesthe same expanding and cooling at the same time. A part of this naturalgas flows into LPC 2, another part—into the inlet branch pipe from thecooling agent side of heat exchanger-refrigerator 6. Partially cooleddown gas under partially reduced pressure passes through heatexchanger-refrigerator 6. Next the natural gas under required pressureis supplied to gas consumer 7.

Another part of gas that was delivered into LPC 2 of the expansion gasturbine performs additional work, reduces pressure and is cooled down.This gas is fed from LPC 2 to the second heat exchanger-refrigerator 8,where gas is heated and cold is taken off. Next natural gas underreduced pressure is supplied to consumer 9. The expansion gas turbinethat includes HPC 1 and LPC 2 rotates electric generator electricgenerator 4. Electric power is supplied to consumer 5.

Cold can be used for freezing chambers, ice rinks etc and forliquefaction of natural gas produced from boreholes. The useful workperformed by gas in the process of expansion can also be used forliquefaction of gas and power supply of a remote natural gas borehole.

Variant 2. (DWG.2)

Utilization power installation includes an expansion gas turbine thatcontains high pressure component 10 (HPC 10), medium pressure component11 (MPC 11) and low pressure component (LPC 12) that are arranged on thesame shaft. The inlet of HPC 10 is connected to high pressure gas mainpipeline 13. The outlet of HPC 10 is connected both to the inlet of MPC11 and to the inlet branch pipe from the cooling agent side of heatexchanger-refrigerator 16. The gas outlet of heat exchanger-refrigerator16 is connected to low pressure gas consumer 17. The outlet of MPC 11 isconnected both to the inlet of LPC 12 and the inlet branch pipe from thecooling agent side of heat exchanger-refrigerator 18. The gas outletfrom heat exchanger-refrigerator 18 is connected to low pressure gasconsumer 19. The outlet of LPC 12 is connected to the inlet branch pipefrom the cooling agent side of heat exchanger-refrigerator 20. The gasoutlet from heat exchanger-refrigerator 20 is connected to low pressuregas consumer 21.

The utilization power installation operates in the following way. Highpressure natural gas flows out of main pipeline 13 into HPC 10, rotatesthe same expanding and cooling at the same time. A part of this naturalgas flows into MPC 11, rotates the same expanding and cooling at thesame time, another part—into the inlet branch pipe from the coolingagent side of heat exchanger-refrigerator 16, from which natural gas issupplied to low pressure gas consumer 17. Pressure required to gasconsumer 17 can be higher than that required to other natural gasconsumers 19 and 21. Another part of the gas flow performs work in MPC11, reduces pressure additionally and is cooled down. Next natural gasflow branches out. One part of this flow is fed to the inlet branch pipefrom the cooling agent side of heat exchanger-refrigerator 18, fromwhich natural gas is supplied to gas consumer 19. The rest part of theflow is fed to the inlet of LPC 12, rotating the same expanding andbeing cooled down at the same time. Then natural gas flows into heatexchanger-refrigerator 20, from which it is fed to low pressure naturalgas consumer 21. The expansion gas turbine rotates electric generator14, that generates current for electric power consumer 15.

Cold can be used for freezing chambers, ice rinks etc and forliquefaction of natural gas produced from boreholes. The useful workperformed by gas in the process of expansion can also be used forliquefaction of gas and power supply of a remote natural gas borehole.

Variant 3. (DWG.3)

The utilization power installation includes high pressure expansion gasturbine 22 (HPT 22), the inlet of which is connected to high pressurenatural gas pipeline 23. The shaft of HPT 22 is connected to electricgenerator 24 kinematically or directly the generator being electricallyconnected with power consumer 25. The outlet of HPT 22 is connected tothe inlet branch pipe from the cooling agent side of heatexchanger-refrigerator 26. The gas outlet of heat exchanger-refrigerator26 is connected to the inlet of the medium pressure expansion gasturbine 27 (MPT 27). The shaft of MPT 27 is connected kinematically ordirectly to electric generator 28, which is connected electrically topower consumer 29. The outlet of MPT 27 is connected to the inlet branchpipe from the cooling agent side of heat exchanger-refrigerator 30. Thegas outlet of heat exchanger-refrigerator 30 is connected to the inletof low pressure expansion gas turbine 31 (LPT 31). The shaft of LPT 31is connected kinematically or directly to electric generator 32, whichis connected electrically with power consumer 33. The outlet of LPT 31is connected to the gas inlet of heat exchanger-refrigerator 34. The gasoutlet of the heat exchanger-refrigerator 34 is connected to lowpressure natural gas consumer 35.

The utilization power installation operates in the following way. Highpressure natural gas is fed from main pipeline 23 to HPT 22, rotatingthe same, expanding and being cooled down. Next gas is supplied from HPT22 to heat exchanger-refrigerator 26, where cold is utilized and gas isheated and expands. Further gas is delivered to MPT 27, rotating thesame, expanding and being cooled down. Next gas flows into heatexchanger-refrigerator 30, where cold is utilized and gas is heated andexpands. Then heated and expanded gas is fed from heatexchanger-refrigerator 30 to LPT 31 rotating the same, expanding andbeing cooled down. Next gas flows from LPT 31 to heatexchanger-refrigerator 34, where cold is utilized and natural gas isheated and expands. Further natural gas is supplied to low pressure gasconsumer 35. HPT 22, MPT 27 and LPT 31 rotate electric generators 24, 28and 32 respectively that supply electric power to consumers 25, 29, 33.Electric generators 24, 28 and 32 can be connected to the commonelectric network

Due to stage-by-stage cooling down of gas in HPT 22, MPT 27 and LPT 31and stage-by-stage heating of the same in heat exchangers-refrigerators26 and 30 total efficiency of utilization power installation increases.

INDUSTRIAL APPLICABILITY

The invention can be used for solving a wide scope of practical problemsof generation of additional energy and non-expensive cold. The inventioncan be used at the outlet of high pressure natural gas directly out ofboreholes and for reduction of gas pressure at the outlet of mainpipelines down to the pressure required by the consumer etc.

In all descriptions of preferred embodiments an expansion gas turbine isused as a gas expansion machine. However a gas expansion machine of anytype can be used, e.g. piston or rotor—type gas expansion machines,including those comprising high pressure and low pressure components orhigh pressure, medium pressure and low pressure components.

Turbines, pumps, ventilators, winches or other converters of mechanicalenergy can be used instead and/or simultaneously with the electricgenerator.

Utilization power installations described in preferred embodiments ofthe invention utilization power installations can be located directlybeside natural gas boreholes if natural gas pressure at the outlet ofthe borehole exceeds pressure required for the gas main pipeline. Inthis case cold can be used for liquefaction of natural gas produced. Theuseful work performed by gas in the process of expansion can be used forliquefaction of gas power supply of a remote natural gas borehole. Theutilization power installations proposed are very efficient in placeswhere gas main pipelines are connected to installations for natural gassupply to big consumers (electric power plants, domestic natural gasnetworks in settlements etc).

1. A power installation comprising: a gas expansion means consisting ofmore than one gas expansion machine part arranged in the direction ofnatural gas pressure drop; at least one converter of mechanical energyhaving a rotor being connected kinematically with the rotor of at leastone gas expansion machine; exchangers-refrigerators being not less thanthe number of the gas expansion machines; and wherein the first gasexpansion machine has an inlet being connected to a high pressurenatural gas source; the outlet of a preceding gas expansion machine isconnected both to the inlet of the next gas expansion machine and to theinlet branch pipe on the cooling agent side of the correspondingexchanger-refrigerator; the outlet branch pipe on the cooling agent sideof at least one exchanger-refrigerator is connected to a low pressurenatural gas means.
 2. A power installation comprising: a gas expansionmeans comprising a high pressure gas expansion machine and a lowpressure gas expansion machine, the inlet of said high pressure gasexpansion machine being connected to a high pressure natural gas source;wherein said high pressure gas expansion machine has an inlet, a firstoutlet and a second outlet, and said low pressure gas expansion machinehas an inlet, a first outlet and a second outlet; a converter ofmechanical energy having a rotor being connected kinematically with arotor of at least one gas expansion machine; a firstexchanger-refrigerator; and wherein the first outlet of the highpressure gas expansion machine is connected both to the inlet of the lowpressure gas expansion machine and to the inlet branch pipe on thecooling agent side of the first exchanger-refrigerator; and the outletbranch pipe on the cooling agent side of the exchanger-refrigerator isconnected to a low pressure natural gas means.
 3. The power installationof claim 1, wherein the high pressure natural gas source is selectedfrom the group comprising: a main pipeline, a high-pressure natural gaspipeline; a medium-pressure natural gas pipeline; a gas pipeline of agas distribution station; a gas pipeline of a power station; a boilerhouse; and a borehole in the natural gas production site.
 4. The powerinstallation of claim 2, wherein the high pressure natural gas source isselected from the group comprising: a main pipeline, a high pressurenatural gas pipeline, a medium pressure natural gas pipeline, a gaspipeline of a gas distribution station, a gas pipeline of a powerstation, a boiler house and a borehole of a natural gas production site,etc.
 5. The power installation of claim 2 further comprising anexchanger-refrigerator installed at the outlet of the low pressure gasexpansion machine.
 6. The power installation of claim 2, wherein therotors of the gas expansion machines are kinematically unconnected witheach other, the rotor of each gas expansion machine is kinematicallyconnected with a rotors of converter of mechanical energy.
 7. The powerinstallation of claim 2, wherein the rotors of the gas expansionmachines are kinematically connected with each other, the rotors of eachgas expansion machine is kinematically connected with a rotor ofconverter of mechanical energy.
 8. The power installation of claim 2,wherein the rotors of the gas expansion machines are kinematicallyconnected with each other, the rotors of each gas expansion machine iskinematically connected with rotor of at least one one converter ofmechanical energy.
 9. The improvement of the power installationaccording to claim 2, wherein the rotors of the gas expansion machinesare kinematically unconnected with each other; the rotors of the eachgas expansion machine is kinematically connected with at least one rotorof converter of mechanical energy.
 10. The improvement of the powerinstallation according to claim 2, wherein the rotors of the gasexpansion machines are mechanically unconnected with each other; therotor of each gas expansion machine is mechanically connected with rotorof converter of mechanical energy.
 11. The improvement of the powerinstallation according to claim 2, wherein the rotors of the gasexpansion machines are mechanically unconnected with each other; therotor of the gas expansion machines is mechanically connected with rotorof converter of mechanical energy.
 12. The improvement of the powerinstallation according to claim 2, wherein the rotors of the gasexpansion machines are mechanically connected with each other; the rotorof the gas expansion machine is mechanically connected with at least oneconverter of mechanical energy.
 13. An improvement of the powerinstallation according to claim 2 wherein the rotors of the gasexpansion machines are kinematically connected with each other; therotors of the gas expansion machines are kinematically connected withrotor of at least one converter of mechanical energy.
 14. The powerinstallation of claim 2 further comprising an exchanger-refrigeratorinstalled at the outlet of the low pressure gas expansion machine.